These are a common and welcome condiment for tacos, tostadas and the like throughout much of Mexico, though people don’t write about them nearly as much as they do the salsas. You can make them with lime, which is very fresh tasting and, I believe, the most common, or with very light vinegar. I’ve occasionally seen a dash of oil added—olive oil would be my choice—which adds a little balancing richness. When manzano chiles are used, they take focus over the onions. When it’s habaneros, so little is used (because of their heat) that most people would call simply call these “spicy pickled onions.” White onions are the most common, but red onions are welcome here too. If you are not planning to use the onions within a day or so, it’s best to pickle them in vinegar. Lime fades in flavor.
Servings: 3cups for manzano chile version, 2 cups for the habanero one
1medium (6 ounce)white onion, sliced 1/8 inch thick
3(about 9 ounces total)manzano (AKA perón) chiles, stemmed, seeded and sliced 1/8 inch thick OR 2 medium (about 3/4 ounce total) habanero chiles, stemmed, seeded and thinly sliced
1/2cup fresh lime juice, plus more if needed OR ¼ cup light vinegar mixed with ¼ cup water (see note below), plus more if needed
In a medium bowl, mix together the onion, chile, oregano and 1/2 teaspoon salt.To avoid wasting a lot of lime or vinegar, pack the mixture into a straight-sided container (a wide-mouth jar works well) and pour on the lime juice or vinegar mixture.Press the vegetables down to ensure that they are nearly submerged.If needed, add more lime or diluted vinegar.Cover and refrigerate for a couple of hours or, preferably, overnight.These will keep for several weeks in the refrigerator.When you’re ready to serve them, remove them from the pickling liquid.
A note about vinegar: Honestly, if you’ve chosen the vinegar version of this dish, any light-flavored vinegar will work—white wine, rice wine, champagne, even distilled white.I’ve written this for one that is the common 5% acidity (listed on most labels). The homemade fruit vinegars sold by fruit and vegetable vendors in Mexican markets can be wonderfully nuanced, but they are usually so light that they need no cutting with water.